As promised, PSA Peugeot Citroën unveiled two prototypes featuring diesel-electric parallel hybrid powertrains, the Peugeot 307 and the Citroën C4 Hybride HDi.

The hybrids deliver average combined city and highway fuel consumption of 3.4 liters per 100 kilometers (69 mpg US), with 90 grams of CO2 emitted per kilometer—a tank-to-wheel record for compact cars, the most popular segment in Europe. This is about 25% better than a similar vehicle equipped with a gasoline hybrid system, or as much as a liter per 100 kilometers in combined city and highway driving.

Hybrid technology using a petrol engine is not very competitive financially, and does not offer significantly better fuel economy or CO2 emission performance than a conventional HDi diesel engine. However, PSA Peugeot Citroën believes that combining a hybrid powertrain with an HDi engine would constitute a step change in terms of improved fuel economy and lower CO2 emissions in Europe, where diesel engines are already widely used.
—PSA Peugeot Citroën statement

PSA Peugeot Citroën’s Hybrid HDi technology includes:

* 1.6-liter HDi engine and diesel particulate filter system (DPFS)
* New-generation Stop & Start system (earlier post)
* Electric motor and inverter
* High-voltage battery pack
* Dedicated control electronics
* All-electric mode for speeds under 50 kilometers an hour (31 mph)
* Driver selection of Extended ZEV (Zero Emission Vehicle, i.e., all-electric) mode
* Electronically-managed gearbox